Axial flow fans



Nov. 21, 1961 J. c. BUSQUET 3,009,630

AXIAL FLOW FANS Filed May 5, 1958 INVENTOR A ORNEY Unite States Thisinvention relates to an axial flow fan, the impeller of which isprovided with hollow blades and the invention has for its object toincrease the output of the fan and to vary the output, if required.

According to the invention the wall of the hollow blades near theoutflow side of the impeller is provided with at least one dischargeopening for a pressure fluid entering the interior of the blade andhaving a pressure exceeding that at the outflow side of the impeller andsaid discharge openings being located at the front face of the blades asviewed in the direction of rotation. With a fan the casing of which iswidened behind the impeller to constitute a diffuser the fluid to beintroduced into the cavity of the impeller blades may be withdrawn fromsaid diffuser.

It appeared that by the discharge of said pressure fluid through theopenings in the blade wall the output of the fan for unchangeddimensions of the impeller is considerably increased. Moreover theoutput of the fan may be varied by adjusting the supply of the pressurefluid entering the hollow blades. It appeared namely that at thepressure side of the blade, where the pressure fluid flows out throughthe holes in the blade wall a more uniform pressure is built up whereasat the low pressure side of the blade the pressure is not increased. Thepres sure fluid flowing out of the opening or openings in the blade wallforms a shield, which apparently prevents the flow of fluid from thepressure side at the rear end of the blade to the low pressure side ofthe blade. The outflowing pressure fluid thereby performs the functionof a pivotal blade part of adjustable blades, so that when varying thesupply of pressure fluid enter-ing in the interior of the blades alsothe output of the impeller is varied. In order to still increase therange of outputs of the fan adjustable guide vanes may be arranged atthe inflow side of the fan casing.

In the accompanying drawing, which illustrates an embodiment of the fanaccording to the invention, FIG. 1 is a longitudinal sectional view ofthe fan.

FIG. 2 is a cross-section taken on the line II-II of FIG. 1 and FIG. 3is a section of two adjacent blades taken on the line III-HI of FIG. 2,the direction of rotation of the impeller being indicated by the arrowa.

The shaft 2 of the impeller 1 having a series of hollow blades 3 at itscircumference, is supported at the suction side in a bearing 4 and atthe pressure side in a bearing 5. The bearing 4 is located in astationary more or less conical body 6 of sheet metal mounted adjacentthe impeller hub and also the bearing 5 is mounted in a stationaryhollow conical body 7.

Adjustable guide vanes 9 are arranged at the inflow side of the casing 8and the casing is conically widened to constitute a ditfusor 10 behindthe impeller 1.

At the apex of the conical body 7 an adjustable valve 11 is mounted,which has its rod 13 connected to an arm of a bell crank lever 12 bymeans of which the valve may be adjusted. When valve 11 is in openposition air-from the difiuser 10 will flow into the hollow body 7 andthrough the hollow impeller hub enter the interior of the hollow blades3 by means of holes 14 provided in the circumferential wall of the hubin order to flow out through a slot 15 at the rear end of each blade. Byadjusting the valve 11 the quantity of air flowing out through the slots15 and, therefore, the output of the fan may be varied. As shown in FIG.3 the air flows out through the slot 15 in a direction substantiallyperpendicular to the front face of the blade.

In order to further increase the pressure of the air entering the hollowblades 3 auxiliary blades 16 are provided in the hollow impeller hub.

What I claim is:

1. An axial flow fan comprising an impeller having a hollow hub with acircumferential wall carrying hollow blades, a casing surrounding saidimpeller and being widened at the discharge side of the impeller toconstitute a diffuser, a stationary hollow conical body within saiddiffuser and adjacent the impeller, said body having an inlet openingand at its end facing the impeller an outlet opening, said hollowimpeller hub having an inlet opening in communication with said outletopening and at least one opening in its circumferential wall and incommunication with each hollow blade, each blade having at least onedischarge opening for the fluid flowing from the interior of saidconical hollow body into the interior of the blade, said dischargeopening being located in the front wall of the blade immediatelyupstream of the trailing edge of the blade as viewed in the direction ofrotation to discharge the fluid which defines a shield disposed at anangle with said front wall.

2. An axial flow fan comprising an impeller having a hollow hub with acircumferential Wall carrying hollow blades, a casing surrounding saidimpeller and being widened at the discharge side of the impeller toconstitute a diffuser, a stationary hollow conical body within saiddiffuser and adjacent the impeller, said body having an inlet openingand at its end facing the impeller an outlet opening, said hollowimpeller hub having an inlet opening in communication with said outletopening and at least one opening in its circumferential wall and incommunication with each hollow blade, and an adjustable valve arrangedat the inlet opening of said hollow conical body, each blade having atleast one discharge opening for the fluid flowing from the interior ofsaid conical hollow body into the interior of the blade, said dischargeopening being located in the front wall of the blade immediatelyupstream of the trailing edge of the blade as viewed in the direction ofrotation to discharge the fluid which defines a shield disposed at anangle with said front wall.

References Cited in the file of this patent UNITED STATES PATENTS2,294,586 Troller Sept. 1, 1942 2,578,478 Janes Dec. 11, 1951 2,599,470Meyer June 3, 1952 2,618,433 Loos et a1. Nov. 18, 1952 2,749,027 StalkerJune 5, 1956 2,759,663 Stalker Aug. 21, 1956 2,830,754 Stalker Apr. 15,1958 2,874,894 Goldschmied Feb. 24, 1959 2,935,245 McDonald May 3, 1960FOREIGN PATENTS 754,579 Great Britain Aug. 8, 1956 802,811 France June22, 1936 1,009,308 France Mar. 5, 1952 1,016,738 France Sept. 3, 1952

